Can't change to a custom gamemode in vanilla gamemodes' main

[DiskPoppy]

I think uberasmtool still thinks it's a vanilla gamemode, so it uses the vanilla table and crashes.

[Fernap]

Presumably line 55 in asm/base/gamemode.asm should be changed to LDA !previous_mode rather than LDA $0100|!addr (haven't actually tested though). previous_mode has already been updated by that point, so it'll jump to the routine for the currently executing mode, rather than the mode that $0100 has been changed to.

That is, unless you want the current mode to be able to be overridden in this way, but that doesn't look like it's intended based on the way what's there is written.